Overhead conveyors are utilized in various production, assembly and treatment environments to transport parts or products through various operational stages. Typically, such conveyors employ a rotating, generally horizontal drive tube or shaft that supports trolleys from which the load is suspended. Wheels on the trolleys ride on the upper surface of the rotating drive tube, and each is mounted for rotation about a driven wheel axis that is non-parallel and non-perpendicular to the drive tube axis, preferably at an acute angle to the drive axis. Overhead conveyors utilizing a drive where the load is suspended beneath the drive tube are disclosed, for example, in U.S. Pat. No. 4,203,511, issued May 20, 1980 to Uhing.
Overhead conveyors of this type, however, are restricted to applications in which the products being transported may be suspended beneath the drive tube. Accordingly, belt conveyors and similar configurations are typically used when it is desired to transport products or materials along a path that is spaced above the conveyor drive. However, belt conveyors do not provide the advantages of conveyors powered by a rotating drive tube in quiet operation and the safety provided by the friction drive which stops the advancement of the conveyed products if resistance to movement is encountered.